Polymeric compositions, derived from copolymers of .alpha.,.beta.,.beta.-trifluorostyrene with a variety of substituted .alpha.,.beta.,.beta.-trifluorostyrenes, in which at least one of the substituents is an ion-exchange moiety have utility as ion-exchange membranes, as disclosed in related U.S. Pat. No. 5,422,411 issued Jun. 6, 1995.
Typically, ion-exchange moieties are introduced into copolymers containing unsubstituted .alpha.,.beta.,.beta.-trifluorostyrene units (so called "base copolymers") via aromatic substitution of at least a portion of those units. This typically involves preparation and purification of the base copolymer, followed by aromatic substitution and subsequent isolation and purification of copolymer containing the ion-exchange moiety. In an alternative approach for introducing ion-exchange functionality, an ion-exchange moiety or masked ion-exchange moiety is present in one or more of the monomers prior to copolymerization. The use of a masked ion-exchange moiety, which can be converted to the corresponding ion-exchange moiety via a simple procedure, can be advantageous.